Week 11 Flashcards
Puberty
Describes the physiological, morphological and behavioural changes as the gonads switch from infantile to adult forms
Physical changes- growth
Adolescent growth spurt: rapid increase in the individuals height (and weight) as a consequence of the action of gonadal sex steroids
Height gain during puberty (average): boys-28cm, girls 25cm
Time minimum growth velocity: girls 9-10. Boys 9-12
Peak height velocity girls: 12 boys:14.
Time of decreasing growth velocity (epiphyseal fusion)
Physical changes: secondary sexual characteristics
Girls:
-breast development: controlled by ovarian oestrogens
-pubic and axillary hair: controlled by ovarian and adrenal androgens
Boys:
-development of penis, scrotum and pubic hair growth
-enlargement of larynx and laryngeal muscles (voice deepening)
-increase body muscle mass: controlled by testicular (and adrenal) androgens
Tanner stages- boys
Stage 1:
-Prepubertal: no pubic hair
-Testicular length <2.5cm
-Testicular volume <3.0ml
Stage 2:
-sparse growth of slightly curly pubic hair, mainly based on of penis
-testes >3ml (>2.5cm in longest diameter)
-scrotum thinning and reddening
Stage 3:
-thicker curlier hair spread to mons pubis
-growth penis in width and length; further growth of testis
Stage 4:
-adult type hair, not yet spread to medial surface thighs
-penis enlarged further; testes larger, darker scrotal skin colour
Stage 5:
-adult type hair spread to medial surface thighs
-genitalia adult size and shape
Tanner stages girls
Stage 1:
-prepubertal: no pubic hair
-elevation of papilla only
Stage 2:
-sparse growth long straight or slightly curly minimally pigmented hair mainly on Labia
-breastbud noted/palpable ; enlargement of areola
stage 3:
-darker, coarser hair spreading over mons pubis
-further enlargement of breast and areola with no separation of contours
Stage 4:
-thick adult type hair not yet spread to medial surface thighs
-projection of areola and papilla to form secondary mound above level breast
Stage 5:
-hair adult type and distributed in classic inverse triangle
-adult contour breast with projection of papilla only
When does puberty start
Boys:
Testicular volume 4mls
97th centile: 10 years
3rd centile: 14 years
Adulthood: 20-25ml
Girls:
Breast stagen Tanner 2
97th centile: 9.2 years
3rd centile: 13.2 years
What is needed for puberty
Sex chromosomes XX/XY
Functioning hypothalamus
Functioning pituitary
End organ function (ovary/testes)
Responsiveness of tissues to hormone
Hormonal changes at puberty
Physical changes:
-controlled by gonadal sex steroids
-regulated by LH and FSH
Orchestration of puberty through GnRH pulse generator (hypothalamus) resulting in pulsatile LH and FSH secretion (pituitary) hypothalamo-pituitary-gonadal axis
Precocious puberty
Onset of secondary sexual characteristics before 8 years (girl), 9 years (boy)
Menarche before 9 years may lead to short stature
May be earlier in some ethnic groups eg African- Caribbean girls
May be concordant (follows normal sequence)- central gonadotrophin activation
Or discordant (eg pubic hair with small testes)- peripheral sex hormone production
Delayed puberty
Absence of secondary sexual characteristics by 13 years (girl), 14 years (boy)
Delayed puberty leads to reduced peak bone mass and osteoporosis
Central precocious puberty
Early activation of pulsatile GnRH regulator therefore early activation of gonadal sex hormone production and action
Incidence 1 in 5000 to 10000
Idiopathic CPP: up to 80% female, only 30% male
Peripheral precocious puberty
GnRH remains silent
Higher levels sex hormones
Derived from gonads or adrenal, or androgen secreting tumours
Adrenarche
Onset of adrenal androgen production due to development/maturation of the ZR
Takes several years until early adolescent where ZR is complete and this results in higher levels of adrenal androgen precursors
Clinical features:
-transient growth acceleration
-pubic/axillary hair
-oily skin, mild acne
-adult type body odor
Adrenarche does not equal pubarche
Onset of Adrenarche independent from regulation of central puberty
Idiopathic premature Adrenarche
Definition: increased adrenal androgen secretion (above sex and age specific reference range before 8 years in girls and 9 years in boys)
And clinical signs of androgen action: pubic/axillary hair, body odor, mild acne, oily skin
Exclude precocious puberty, enzyme defect, virilising tumours
GnRH (LHRH) test
The test: IV injection of 100mcg GnRH analogue with blood sampling for LH and FSH at baseline and 30’ and 60’ after
Central PP: stimulation pubertal range. Stimulated LH:FSH ratio>1
Peripheral PP: stimulation prepubertal range or suppression. Stimulated LH:FSH <1
Causes central precocious puberty GnRH dependent
Idiopathic precocious puberty
CNS tumours: optic glioma associated with NF1, hypothalamic astrocytoma
CNS disorders: developmental abnormalities, hypothalamic hamartoma, encephalitis, Brain abscess, hydrocephalus, myelomeningocele, arachnoid cyst, vascular lesion, cranial irradiation
Secondary central precocious puberty ie CAH
Psychosocial
Causes peripheral precocious puberty GnRH independent
Increased androgen secretion: congenial adrenal hyperplasia (21OHD, 11OHD), virilising neoplasm, leydig cell adenoma, familial male precocious puberty- testotoxicosis
Gonadotropin secreting tumours: chorioepitheliomas, germinoma, teratoma, hepatoma, choriocarcinoma
McCune-Albright syndrome
Ovarian cyst
Oestrogen secreting neoplasm
Hypothyroidism
Iatrogenic or exogenous sex hormones
Consequences of early puberty
Psychological problems may arise as a result of:
-pubertal levels of sex steroids resulting in adolescent behaviour
-altered self image
-child expected to behave at appropriate to height age
Growth:
-fixed amount of growth in puberty means that although the child may present with tall stature, growth will finish early and final height is restricted
Metabolic:
-increasing evidence that children with PP develop long term metabolic complications (glucose intolerance/ diabetes, cardiovascular etc)
Treatment gonadotrophin-dependent (central) PP
Long acting GNRH analogues
-ie decapeptyl :IM injection every 12-10 weeks
-cessation of FSH and LH secretion
No evidence of long term adverse affects
Only evidence of benefit for adult height if onset <6 years
Decision re who is treated is individual- ability to cope with physical and emotional changes of puberty
Usually discontinues when of pubertal age
Delayed puberty
Absence of secondary sexual characteristics by 13 girl 14 boy
First period after 15 years age
May also be pubertal failure “arrest” when puberty begins but fails to progress adequately